Modulating Molecular Interaction of Benzimidazole Derivatives Via Isomerization Toward Rational Additive Engineering for Printable Mesoscopic Perovskite Solar Cells

Abstract

Defect states at the boundaries and the perovskite/electron transport layer (ETL) interface critically induce charge recombination in printable mesoscopic perovskite solar cells (p-MPSCs). Herein, we engineer the defect management by introducing two multifunctional benzimidazole derivative additives, 1H-benzimidazole-2-carboxylicacid (2-CBIm) and 5-benzimidazolecarboxylic acid (5-CBIm), which are isomers with different functional group positions, for improving the performance of p-MPSCs. The functional group position differences modulate the defect passivation ability of 2-CBIm and 5-CBIm in p-MPSCs. 5-CBIm, featuring desired distribution of the carboxyl group and the imidazole group, presents superior binding with perovskite and the TiO₂ ETL than 2-CBIm, whose interaction ability is influenced by the steric effect. The enhanced interaction facilitates defect passivation and nonradiative recombination suppression in p-MPSCs. Consequently, the 5-CBIm device achieves a well-improved champion power conversion efficiency (PCE) of 20.61%, surpassing the 2-CBIm device (19.40%) and the control device (18.17%). This work contributes to a better understanding of structure–property relationships and opens extended possibilities for designing advanced defect passivation additives.